Fiber mat and process of making same

ABSTRACT

A fiber mat of improved tensile strength and a process of making same is disclosed. The fiber mat comprises: fibers; a resinous fiber binder; and a binder modifier comprising a dibasic unsaturated acid.

CROSS-REFERENCE TO RELATED U.S. PATENT APPLICATION

This application claims priority to provisional application Ser. No.60/737,173, filed Nov. 16, 2005.

FIELD OF THE INVENTION

Embodiments of the present invention relate to a fiber mat and processof making same.

BACKGROUND OF THE INVENTION

High strength fiber mats have become increasingly popular in thebuilding materials industry. Most commonly used in roofing shingles,fiber mats have numerous other material applications, including use inroofing, siding and floor underlayment; insulation facers; floor andceiling tile; and vehicle parts.

Various fiber mats and methods of making same have been described. Forexample, U.S. Pat. No. 4,135,029 describes a glass fiber mat made by awet-laid process. Glass fiber mats made by the wet-laid process areformed from glass fibers held together by a binder material. Typically,in wet process glass fiber mats, the binder is applied in a liquid formand dispersed onto the glass fibers by a curtain type applicator.Conventional wet processes strive to produce a uniform coating of binderon the glass fibers. After the binder and glass fibers have been driedand cured, the glass fiber mat is then cut as desired.

A major problem in the manufacture and use of some known fiber mats isinadequate tensile strength. Inadequate tensile strength can causeinterruption in roofing manufacture, and may reduce the ability of thefinished roofing product to resist stresses during service on the roof.Because building materials, generally, and roofing shingles, inparticular, are often subjected to a variety of weather conditions, thefiber mats must also maintain their strength characteristics under awide range of conditions.

For example, the tensile strength of a shingle at low temperature mayhave a significant impact on the performance of the shingle in coldweather. Similarly, high temperatures can affect shingle performance.The tensile strength over these temperature ranges may depend on theadhesion of the fibers to the fiber binder system, the mechanicalproperties of the binder system, and the interaction of the fiber matswith asphalt.

Various embodiments of the present invention may be suitable for use asa component of building materials, and other applications. Variousembodiments may provide a material having improved tensile strengthunder a variety of conditions. In addition, the process of making fibermats in accordance with some embodiments of the present invention mayprovide a fiber mat having improved tensile strength. Additionaladvantages of embodiments of the invention are set forth, in part, inthe description which follows and, in part, will be apparent to one ofordinary skill in the art from the description and/or from the practiceof the invention.

SUMMARY OF THE INVENTION

Responsive to the foregoing challenges, we have developed an innovativefiber mat for use in a building material, the mat comprising: aplurality of fibers; a resinous fiber binder coating the fibers; and abinder modifier comprising from about 0.05 wt. % to about 20 wt. %,based on the weight of the binder, the binder modifier comprising acarboxylic acid.

We have further developed an innovative fiber mat for use in a buildingmaterial, comprising: a plurality of glass fibers; and a fixativecomposition comprising a fiber binder and between about 0.05 wt. % andabout 20 wt. %, based on the weight of the binder, and a binder modifiercomprising a carboxylic acid.

We have developed an innovative process of making a fiber mat for use ina building material, the process comprising the steps of: (a) forming anaqueous fiber slurry; (b) removing water from the fiber slurry to form awet fiber mat; (c) saturating the wet fiber mat with an aqueous solutionof a fiber binder; (d) spraying the wet fiber mat with a binder modifiercomprising a carboxylic acid, and (d) drying and curing the wet fibermat to form a fiber mat product. In one embodiment, the fiber binder andthe binder modifier may be mixed together and applied in a single step.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory only,and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a SEM image of Sample 1 and Sample 2.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The fiber mat of the present invention may comprise a plurality offibers coated or impregnated with a fixative composition. The fixativecomposition may comprise a resinous fiber binder, and a binder modifiercomprising between about 0.05 wt. % and about 20.0 wt. % of a carboxylicacid, based on the fiber binder weight.

In one embodiment, an example of the carboxylic acid that can be used ismaleic acid. In addition to the other ranges mentioned previously, themaleic acid may also comprise a concentration of between about 1 wt. %and about 3 wt. %, based on the weight of the binder. The maleic acidmay be a commercially available acid supplied by, for example, Hunstman.As will be apparent to those of ordinary skill in the art, othercommercially or non-commercially available carboxylic acids may be usedwithout departing from the scope and spirit of the present invention.For example, carboxylic acids that may be used include, but are notlimited to, formic acid, acetic acid, propionic acid, benzoic acid,butyric acid, acrylic acid, lactic acid, glycolic acid malic acid, allamino acids, oxalic acid, malonic acid, succinic acid, glutaric acid,adipic acid, and salicylic acid.

The binder modifier may comprise a substantially pure carboxylic acid.Alternatively, in one embodiment, the modifier may further comprise asecondary binder modifier. The secondary binder modifier may comprise,for example, polyurethane, styrenebutadiene, and/or acrylic. Thesecondary binder modifier may be incorporated with the binder modifieras a composition, or may be added separately. In one embodiment of thepresent invention, the secondary binder modifier may comprise less thanabout 15 wt. %, based on the total weight of the binder solids.

The fiber binder may comprise between about 5 wt. % and about 30 wt. %,based on the fiber mat product weight. In one embodiment of the presentinvention, the fiber binder may comprise a formaldehyde type resin. Thefiber binder may include, but is not limited to, a urea/formaldehyderesin, a phenol/formaldehyde resin, a melamine/formaldehyde resin,and/or a mixture thereof. It is contemplated, however, that otherbinders, such as, for example, ethylene vinyl acetate, and other knownresins adapted for binding mat fibers may be used without departing fromthe scope and spirit of the present invention.

In one embodiment of the present invention, the urea-formaldehyde resinis a commercially available material, such as, for example, GP2997supplied by Georgia Pacific Resins, Inc.; Dynea 246 from Dynea Co.; andBorden FG 486D from Borden Chemical Inc. Other commercial formaldehyderesins may include PR-913-23, supplied by Borden Chemical, Inc. As willbe apparent to those of ordinary skill in the art, other commercially ornon-commercially available binders may be used without departing fromthe scope and spirit of the present invention.

The resinous fiber binder may contain methylol groups which, uponcuring, form methylene or ether linkages. These methylols may include,for example, N,N′-dimethylol; dihydroxymethylolethylene;N,N′-bis(methoxymethyl), N,N′-dimethylol-propylene;5,5-dimethyl-N,N′-dimethylolpropylene; N,N′-dimethylolethylene;N,N′-dimethylolethylene and the like.

The fiber binder and the binder modifier are adapted to be compatible.The components may be intimately admixed in an aqueous medium to form astable emulsion which may not become overly gummy, or gel, even afterstorage for periods of 24 hours or longer. This may be advantageous inpractical commercial use of the composition. It is contemplated thatindividual aqueous mixtures for binder and modifier may be used inembodiments of the present invention.

In one embodiment of the present invention, the fibers comprise glassfibers. The glass fibers may comprise individual fiber filaments havingan average length in the range of, but not limited to, from about ¼ inchto about 3 inches, and an average diameter in the range of, but notlimited to, from about 5 to about 50 micrometers (μm). It iscontemplated, however, that the glass fibers may be in another form,such as, for example, a continuous strand or strands. In an alternativeembodiment of the present invention, the fibers may comprise otherfibers, including, but not limited to, wood, polyethylene, polyester,nylon, polyacrylonitrile, and/or a mixture of glass and one or moreother fibers. In one embodiment, the fiber mat may further comprise asmall amount of filler, e.g. less than about 0.5%, based on the fiberweight. A fiber mixture may be optional for construction materialapplication, such as, for example, roofing and siding, because excessiveamounts of filler may reduce porosity and vapor ventability of the fibermat.

In the finished cured mat product, the fiber content may be in the rangeof from about 55 wt. % to about 98 wt. %. In one embodiment of thepresent invention, the fiber content is more particularly in the rangeof from about 66 wt. % and about 88 wt. %. The binder modifier contentmay be in the range of from about 0.05 wt. % to about 45 wt. %. In oneembodiment of the present invention, the binder modifier content is moreparticularly in the range of from about 15 wt. % to about 30 wt. %.

In one embodiment of the present invention, the fibers may be formedinto a mat with the aid of a dispersing agent. The fiber dispersingagent may comprise, for example, tertiary amine oxides (e.g.N-hexadecyl-N,N-dimethyl amine oxide), bis(2-hydroxyethyl) tallow amineoxide, dimethyl hydrogenated tallow amine oxide, dimethylstearyl amineoxide and the like, and/or mixtures thereof. As will be apparent tothose of ordinary skill in the art, other known dispersing agents may beused without departing from the scope and spirit of the presentinvention. The dispersing agent may comprise a concentration in therange of from about 10 ppm to about 8,000 ppm, based on the amount offiber. The dispersing agent may further comprise a concentration in therange of from about 200 ppm to about 1,000 ppm, based on the amount offiber.

In one embodiment, the fibers may be formed into a mat with the aid ofone or more viscosity modifiers. The viscosity modifier may be adaptedto increase the viscosity of the composition such that the settling timeof the fibers is reduced and the fibers may be adequately dispersed. Theviscosity modifier may include, but is not limited to, hydroxyl ethylcellulose (HEC), polyacrylamide (PAA), and the like. As will be apparentto those of ordinary skill in the art, other viscosity modifiers may beused without departing from the scope and spirit of the presentinvention.

The process of making a fiber mat in accordance with one embodiment ofthe present invention will now be described. The process will bedescribed with particular reference to a wet-laid process. It iscontemplated, however, that other processes known in the art, such as,for example, a dry-laid process, may be used without departing from thescope and spirit of the present invention. Furthermore, the process isdescribed using chopped bundles of glass fibers. As discussed above,however, other types of fiber content are considered well within thescope of the present invention.

The process of forming glass fiber mats according to one embodiment ofthe present invention comprises adding chopped bundles of glass fibersof suitable length and diameter to an aqueous medium to form an aqueousfiber slurry. As discussed above, the aqueous medium may include asuitable dispersing agent. A viscosity modifier or other process aid mayalso be added to the water/dispersing agent medium. From about 0.05 toabout 0.5 wt. % viscosity modifier in white water may be suitably addedto the dispersant to form the slurry.

The glass fibers may be sized or unsized, and may be wet or dry, as longas they are capable of being suitably dispersed in the water/dispersingagent medium. The fiber slurry, containing from about 0.03 wt. % toabout 8 wt. % solids, is then agitated to form a workable dispersion ata suitable and uniform consistency. The fiber slurry may be additionallydiluted with water to a lower fiber concentration to between about 0.02wt. % and about 0.08 wt. %. In one embodiment, the fiber concentrationmay be more particularly diluted to about 0.04 wt. % fiber. The fiberslurry is then passed to a mat-forming machine such as a wire screen orfabric for drainage of excess water. The excess water may be removedwith the assistance of vacuum.

The fibers of the slurry are deposited on the wire screen and drained toform a fiber mat. The fiber mat may then be saturated with an aqueoussolution of binder. The aqueous binder solution may comprise, forexample, from about 10 wt. % to about 40 wt. % solids. The fiber mat maybe soaked for a period of time sufficient to provide the desiredfixative for the fibers. Excess aqueous binder solution may then beremoved, preferably under vacuum.

The formed fiber mat may then be sprayed with the binder modifier, suchas maleic acid, to achieve the desired concentration. An aqueoussolution of maleic acid may be used to obtain a uniform distributionover the binder treated fibers. In one embodiment of the presentinvention, either before or after applying the binder modifier, thefiber mat may be compressed, for example by passing it between rollersor another compressing device, to reduce mat thickness for curing. Inaddition to spraying, this invention also contemplates neutralizing theacid with a base such as ammonia and adding it into binder solution toavoid gelling. It is believed that the ammonia will volatize at highcuring temperature and the acid form will return.

After treatment with binder or binder/modifier composition, if desired,the mat is then dried and the fixative composition may be cured in anoven at an elevated temperature. A temperature in the range of about160° C. to about 400° C., for at least about 2 seconds, may be used forcuring. In one embodiment, a cure temperature in the range of about 225°C. to about 350° C. may be used. It is contemplated that in analternative embodiment of the present invention, catalytic curing may beprovided with an acid catalyst, such as, for example, ammonium chloride,p-toluene sulfonic acid, or any other suitable catalyst.

The combination of the maleic acid and binder used in variousembodiments of the present invention may provide several advantages overcurrent binder compositions. For example, the tensile strength of themat may be increased. In addition, the tensile strength of the mat maybe increased at lower temperatures to minimize cracking and failure.Other advantages will be apparent to one of ordinary skill in the artfrom the above detailed description and/or from the practice of theinvention.

Having generally described various embodiments of the present invention,reference is now made to the following examples which illustrateembodiments of the present invention and comparisons to a controlsample. The following examples serve to illustrate, but are not to beconstrued as limiting to, the scope of the invention as set forth in theappended claims.

EXAMPLE 1

Part A. In a vessel at room temperature, under constant agitation, 5.16g of chopped bundles of glass fibers, each having an average 30-40 mmlength and 8-16 micrometer diameter, were dispersed in 12 liters ofwater containing 800 ppm of N-hexadecyl-N,N-dimethylamine oxide toproduce a uniform aqueous slurry of 0.04 wt. % fibers. The fiber slurrywas then passed onto a wire mesh support with dewatering fabric, andvacuum was applied to remove excess water and to obtain a wet matcontaining about 60% fibers.

Part B. A binder composition was prepared by diluting urea/formaldehyderesin binder (UF) with water to a 24 wt. % solids solution. The wetglass mat, suspended on the wire mesh, then was soaked in the bindercomposition, and excess binder was removed by reapplying vacuum. Theresultant wet glass mat weight, with binder applied, was around 10.5grams. One wet glass mat containing fibers and binder was sprayed withan aqueous solution of maleic acid to provide a maleic acidconcentration of 2% with respect to binder. For comparison purposes,another sample was prepared as described in Parts A and B, however theUF binder was used alone without maleic acid modification.

Part C. All samples were dried and cured at 300° C. to obtain dry glassmats weighing about 92 g/m², and containing about 24 wt. % binder. Ittook 9 seconds to cure plain UF, but it took only 5 seconds to cure theacid modified samples. The tensile strengths of the mats were tested onan Instron® Tensile Machine at room temperature. The results of thesetests are recorded in the Tables 1. TABLE 1 Cure Binder Time @ Mat MatBreak Tensile Tensile Sample Weight Maleic 300° C. Caliper Caliper LoadStrength Strength No. (g/m²) Binder Acid (Sec) (mm) Reduction % (N/50mm) (MPa) Increase 1 92.4 GP2997 None 9 1.07 258 4.82 2 92.6 GP2997 2% 50.94 12% 252 5.36 11%

EXAMPLE 2

Part A. In a vessel at room temperature, under constant agitation, 5.16g of chopped bundles of glass fibers, each having an average 30-40 mmlength and 8-16 micrometer diameter, were dispersed in 12 liters ofwater containing 800 ppm of N-hexadecyl-N,N-dimethylamine oxide toproduce a uniform aqueous slurry of 0.04 wt. % fibers. The fiber slurrywas then passed onto a wire mesh support with dewatering fabric, andvacuum was applied to remove excess water and to obtain a wet matcontaining about 60% fibers.

Part B. 11% aqueous solutions of maleic acid and of citric acid wereneutralized with ammonia to pH 8. Then the neutralized maleicacid-ammonium salt or citric acid-ammonium salt was added into a UFresin solution in a 99.5/0.5 dry ratio of UF to the acid-ammonium salt.A binder composition was prepared by diluting the maleic or citrictreated urea/formaldehyde resin binder (UF) with water to a 24 wt. %solids solution; The wet glass mat, suspended on the wire mesh, then wassoaked in the binder composition, and excess binder was removed byreapplying vacuum. The resultant wet glass mat weight, with binderapplied, was around 10.5 grams. A sample was prepared following the sameprocedure with no acid modification for comparison.

Part C. All samples were dried and cured at 300° C. to obtain dry glassmats weighing about 92 g/m², and containing about 24 wt. % binder. Ittook 9 seconds to cure plain UF, but it took only 5 seconds to cure theacid modified samples. The tensile strengths of the mats were tested onan Instron® Tensile Machine at room temperature. The results of thesetests are recorded in Table 2. TABLE 2 Organic Cure Binder Acid- Time @Mat Mat Break Tensile Tensile Sample Weight Ammonium 300° C. CaliperCaliper Load Strength Strength No. (g/m²) Binder Salt (Sec) (mm)Reduction % (N/50 mm) (MPa) Increase 1 93.9 GP2997 None 9 1.02 284 5.582 92.0 GP2997 0.5% 5 0.92 9% 271 5.88  5% Maleic Acid- Ammonium Salt 392.9 GP2997 0.5% Citric 5 0.98 4% 311 6.37 14% Acid- Ammonium Salt

From SEM images shown in FIG. 1, we can tell the thicker mat is mainlycontributed by bubbles which are likely caused by the volatile sideproducts generated during the condensation reactions of UF resin. It isbelieved that carboxylic acids act as both catalysts and reactants todrive the equilibrium condensation reaction to right side for completionand also capture the volatile species to avoid the bubbles forming inthe mat. Therefore, the mat caliper is reduced.

It will be apparent to those skilled in the art that various othermodifications and variations can be made in the construction,configuration, and/or operation of the present invention withoutdeparting from the scope or spirit of the invention. Embodiments of thefiber mat may be used in a building material including, but not limitedto, shingles, underlayment, insulation facers, floor and ceiling tile,vehicle parts, and/or any other suitable building material. Thus, it isintended that the present invention cover all such modifications andvariations of the invention, provided they come within the scope of theappended claims and their equivalents.

1. A fiber mat for use in a building material, said mat comprising: aplurality of fibers; a resinous fiber binder coating said fibers; and abinder modifier comprising a carboxylic acid.
 2. The fiber mat of claim1, wherein said resinous fiber binder comprises a formaldehyde typebinder.
 3. The fiber mat of claim 2, wherein said formaldehyde typebinder is selected from the group consisting of: a urea/formaldehydebinder, a phenol/formaldehyde binder, and a melamine/formaldehydebinder.
 4. The fiber mat of claim 1, wherein the concentration of saidfibers in said mat is between about 55 wt. % and about 98 wt. %.
 5. Thefiber mat of claim 1, wherein said fibers comprise glass fibers.
 6. Thefiber mat of claim 1, wherein the carboxylic acid is maleic acid orcitric acid.
 7. The fiber mat of claim 1, wherein the carboxylic acid isselected from the group consisting of: formic acid, acetic acid,propionic acid, benzoic acid, butyric acid, acrylic acid, lactic acid,glycolic acid malic acid, all amino acids, oxalic acid, malonic acid,succinic acid, glutaric acid, adipic acid, and salicylic acid.
 8. Thefiber mat of claim 7, wherein said formaldehyde type binder is selectedfrom the group consisting of: a urea/formaldehyde binder, aphenol/formaldehyde binder, and a melamine/formaldehyde binder.
 9. Thefiber mat of claim 6, wherein the concentration of said fibers in saidmat is between about 55 wt. % and about 98 wt. %.
 10. The fiber mat ofclaim 6, wherein said fibers comprise glass fibers.
 11. The fiber mat ofclaim 1 further comprising of a secondary binder modifier selected fromthe group of polyurethane, styrenebutadiene, and acrylic.
 12. A fibermat for use in a building material, comprising: a plurality of glassfibers; and a fixative composition comprising a fiber binder and betweenabout 0.05 wt. % and about 20 wt. % binder modifier, based on the weightof the binder, wherein the binder modifier comprises a carboxylic acid.13. The fiber mat of claim 12, wherein the concentration of the fiberbinder, based on the weight of the fibrous mat, is in the range of fromabout 5 wt. % and about 30 wt. %.
 14. The fiber mat of claim 12, whereinsaid glass fibers comprise a plurality of glass filaments having anaverage length of from about 0.25 to about 3 inches and a diameter offrom about 5 to about 50 micrometers.
 15. The fiber mat of claim 14,wherein the concentration of said glass filaments is between about 55and about 98 wt. %.
 16. The fiber mat of claim 12, wherein said fiberbinder comprises a formaldehyde type binder selected from the groupconsisting of: a urea/formaldehyde binder, a phenol/formaldehyde binder,and a melamine/formaldehyde binder.
 17. The fiber mat of claim 12,wherein the carboxylic acid is maleic acid or citric acid.
 18. The fibermat of claim 17, wherein the concentration of the fiber binder, based onthe weight of the fibrous mat, is in the range of from about 5 wt. % andabout 30 wt. %.
 19. The fiber mat of claim 17, wherein said glass fiberscomprise a plurality of glass filaments having an average length of fromabout 0.25 to about 3 inches and a diameter of from about 5 to about 50micrometers.
 20. The fiber mat of claim 17, wherein the concentration ofsaid glass filaments is between about 55 and about 98 wt. %.
 21. Thefiber mat of claim 17, wherein said fiber binder comprises aformaldehyde type binder selected from the group consisting of: aurea/formaldehyde binder, a phenol/formaldehyde binder, and amelamine/formaldehyde binder.
 22. The fiber mat of claim 12, wherein thecarboxylic acid is selected from the group consisting of: formic acid,acetic acid, propionic acid, benzoic acid, butyric acid, acrylic acid,lactic acid, glycolic acid malic acid, all amino acids, oxalic acid,malonic acid, succinic acid, glutaric acid, adipic acid, and salicylicacid.
 23. The fiber mat of claim 12 further comprising of a secondarybinder modifier selected from the group of polyurethane,styrenebutadiene, and acrylic.
 24. A process of making a fiber mat foruse in a building material, said process comprising the steps of: (a)forming an aqueous fiber slurry; (b) removing water from the fiberslurry to form a wet fiber mat; (c) saturating the wet fiber mat with anaqueous solution of a fiber binder; (d) spraying the wet fiber mat witha binder modifier comprising a carboxylic acid, and (d) drying andcuring the wet fiber mat to form a fiber mat product.
 25. The process ofclaim 24, wherein the aqueous fiber slurry further comprises a fiberdispersing agent.
 26. The process of claim 24, wherein the bindermodifier is maleic acid or citric acid.
 27. The process of claim 24,wherein the binder modifier is selected from the group consisting of:formic acid, acetic acid, propionic acid, benzoic acid, butyric acid,acrylic acid, lactic acid, glycolic acid malic acid, all amino acids,oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid,and salicylic acid.
 28. The process of claim 24, wherein the aqueousfiber slurry further comprises a fiber dispersing agent.
 29. The processof claim of claim 24, wherein the binder modifier further comprises of asecondary binder modifier selected from the group of polyurethane,styrenebutadiene, and acrylic.